<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
		<title>Insert title here</title>
		<script type="text/javascript">
		<!--
			function dasalibitaCampos(){
				document.getElementById('numeroCNH').disabled = true;
			}
			function dasabilitaCampoCNH(){
				var idade = document.getElementById('idade').value;
				if(idade > 16){
					document.getElementById('numeroCNH').disabled = false;
				}
				//document.getElementById('nome').display = 'none';
			}
		//-->
		</script>
	</head>
	<body onload="dasalibitaCampos()">
		<form>
			Nome <input type="text" id="nome"><br>
			Idade <input type="text" id="idade" onchange="dasabilitaCampoCNH()"><br>
			Numero CNH <input type="text" id="numeroCNH"><br>
		</form>
	</body>
</html>